基于LED可见光波分复用的音频传输演示仪

利用LED高频率闪烁的响应特性,设计了一种基于LED可见光波分复用的音频传输演示仪。波分复用是让不同波长的可见光同时加载不同信号,通过同一信道传输信息的通信技术。本装置实现了可见光通信技术和波分复用技术的结合,可以大大提高可见光通信的效率。装置亦可用于课堂演示。     

室内LED可见光通信的分集接收系统

根据分集接收的原理,采用选择合并的方式设计了应用于LED可见光通信的信号选择接收装置.理论分析和测量结果表明:该装置能增加信道的数量并自动选择出信噪比最大的信号,可以有效地避免信道中断.     

微波反射光电导衰减法测少子寿命演示实验

采用微波反射光电导衰减法设计了测试少子寿命的演示实验装置.实验装置主要由脉冲激光源、微波发射接收和数据采集处理系统等部分组成.该实验可以直观地演示非平衡载流子随时间的衰减过程,定量给出少子寿命、扩散系数和扩散长度.     

瑞利散射演示实验的改进

蛋白玻璃的主要成分为二氧化硅,内部含有大量无规则分布的纳米气泡,其尺寸远小于可见光的波长.以蛋白玻璃为散射介质,对现有的瑞利散射演示实验进行改进,可以演示介质厚度改变对散射光和透射光的影响,并对比分析瑞利散射光的偏振特性.实验装置简单,易于操作,实验现象直观.     

一个联系应用的演示实验

过去教学中联系生产实际的应用演示很少,但这是一个很重要的环节,不使学生看看实际应用,是无法与生产联系好的。将来学生在生产斗爭中就不能灵活运用所学过的物理知识。我感到加強这方面的演示实验也是教改中很重要的一项任务。现就电磁振荡和电磁波一章讲过后所做的联系应用的演示实验简介如下。演示简单无线电报的发送和接收,可用米波发射机加调制器发送讯号,并用带有灯光讯号的接收机接收。在演示过之后,就提出在生产中的重要应用是无线电操纵。前者装置简单第2期     

室内MIMO可见光通信的接收特性

建立了一种基于MIMO的室内二次反射可见光通信的信道模型。通过模型仿真,从不同位置处接收面上探测器的不同间距、不同面积以及接收面横向、纵向旋转方面,分析了室内MIMO可见光通信的接收特性。仿真结果表明,在满足信号可恢复的条件下,接收面探测器间距d的变化对光信号接收的影响很小,不同接收位置的接收信噪比(SNR)也呈现不同的分布。另外,接收面横向旋转不会影响光信号接收,而纵向旋转具有一定的限制范围。     

基于可见光通信的“水流传声”实验

针对现有中学教材只能演示光在弯曲水流柱中传导而不能展示光携带信息的过程,设计了基于LED可见光通信原理的"水流传声"实验系统.该实验以变曲水流柱为导光载体,借助可见光传递电声信号,可同时演示光在弯曲介质中传导和光携带声音信号的双重过程,便于学生深入理解光通信的本质.     

适合自主探究式学习的光纤传感器组合演示装置

介绍了自行研制的光纤传感器组合演示装置,探索建立基于现代教育理念的演示实验教学模式,阐述该类演示装置在整个专业课程体系中的地位和作用.     

可见光的薄片衍射

本文首先叙述衍射薄片的制备方法，然后详细分析和讨论可见光的薄片衍射及其分辨本领．这种薄片衍射除可用来测定可见光的波长外，还可用来研究可见光谱的精细结构，并且能直接用于课堂演示，有利于提高教学质量，同时薄片的制备简单，易于普遍推广．     

红外线演示实验的再改进

本刊第14卷第4期发表的《实验改进二则》一文中关于红外线反射演示实验仍有两点不妥，讨论如下．原文实验装置如图1，“使铁球位于凹面镜的焦点附近，用烧瓶接收红外线，可以看到红墨水柱沿型管（向外）移动（瓶内空气受热膨胀）．如果取走四面镜，则红墨水柱停止移动（或移动速度十分显著的缓慢）．”以出来说明红外线跟可见光一样是能够被反射的证据明显不够充足．1．虽然铁球放置在四面镜的焦点附近，但由于铁球直径较大（直径为3—5cm，不像光学中的点光源），到达烧瓶的红外线不能理解为全部是来自于四面镜反射的红外线．实际上烧瓶接…     

A tutorial on laser-based lighting and visible light communications:device and technology [Invited]

This tutorial focuses on devices and technologies that are part of laser-based visible light communication(VLC)systems. Laser-based VLC systems have advantages over their light-emitting-diode-based counterparts, including having high transmission speed and long transmission distance. We summarize terminologies related to laser-based solid-state lighting and VLC, and further review the advances in device design and performance.The high-speed modulation characteristics of laser diodes and superluminescent diodes and the on-chip integration of optoelectronic components in the visible color regime, such as the high-speed integrated photodetector,are introduced. The modulation technology for laser-based white light communication systems and the challenges for future development are then discussed.     

A cooperative positioning with Kalman filters and handover mechanism for indoor microcellular visible light communication network

We propose a novel handover scheme for indoor microcellular visible light communication (VLC) network. With such a scheme, the room, which is fully coverage by light, is divided into several microcells according to the layout of light-emitting diodes (LEDs). However, the directionality of light arises new challenges in keeping the connectivity between the mobile devices and light source under the mobile circumstances. The simplest solution is that all LEDs broadcast data of every user simultaneously, but it wastes too much bandwidth resource, especially when the amount of users increases. To solve this key problem, we utilize the optical positioning assisting handover procedure in this paper. In the positioning stage, the network manager obtains the location information of user device via downlink and uplink signal strength information, which is white light and infrared, respectively. After that, a Kalman filter is utilized for improving the tracking performance of a mobile device. Then, the network manager decides how to initiate the handover process by the previous information. Results show that the proposed scheme can achieve low-cost, seamless data communication, and a high probability of successful handover.     

基于离子注入隔离的微缩化发光二极管阵列性能

基于F离子注入隔离技术实现一种新型微缩化发光二极管(micromicro-LED)阵列器件,并系统研究注入能量及发光孔径对micro-LED阵列器光电性能的影响.研究结果表明:相比于F离子50 ke V单次注入器件, 50/100 ke V两次注入器件具有更好的光电性能,器件反向漏电降低8.4倍,光输出功率密度提升1.3倍.同时,在不同的发光孔径(6, 8, 10μm)条件下,器件反向漏电流均为3.4×10–8 A,但正向工作电压随孔径增大而减小,分别为3.3, 3.1, 2.9 V.此外,器件不同发光孔径的有效发光面积比(实际发光面积与器件面积之比)分别为85%, 87%, 92%.与传统台面刻蚀micro-LED器件相比,离子注入隔离技术实现的micro-LED器件具有较低反的向漏电流密度、较高的光输出密度及有效发光面积比.     

Visible light communication system based on spread spectrum technology for intelligent transportation

In recent years, with the rapid development of the solid state Light emitting diodes (LED’s) material, visible light communication has vast applications in transportation system. Generally, LED visible light communication refers to the communication technology which utilizes LED as a signal transmitter, the air as a transmission medium, and the photodiode as a signal receiving component. Visible light communication based on LED light source has been widespread concerned in intelligent transportation system (ITS). In particular, it is used to solve the communication problems between traffic lights and vehicles. However, signal source switching always puzzles the application of visible light communication based on LED in ITS. If signal source switching is not solved effectively, it will result in the interruption of information transmission. The paper proposes a visible light communication system using spread spectrum technology and pulse position modulation. When the vehicle is at the crossroads, the receiver on the vehicle receives signals from the four LED traffic lights at the same time. During the movement of the vehicle, the peak value of the four signals received by the receiver is constantly changing. The receiver detects the relevant peaks from the four traffic light signals and communicates with the traffic lights which have the maximum correlation peak. The problem of signal source switching is solved effectively. The experimental results show that the proposed system can achieve seamless switching between four-way LED traffic lights at the crossing, and the bit error rate of the system is 10^?4–10^?7.     

频率驱动液晶光阀的电光特性研究

讨论了液晶光阀频率驱动方式的原理,并分析了液晶光阀在频率驱动方式下的电光特性.在特定的交流电压下改变外加电场频率,测量了TB3639型液晶光阀在频率驱动方式下的电光特性关系曲线.测量结果表明,TB3639液晶光阀在可见光区域具有电光显示灰度变化特性,不仅能实现黑白显示,也能实现不同灰度级显示.频率驱动方式在可见光的范围内对不同波长的透射率变化趋势影响大致相同,在应用中可避免出现色差较大的现象.这种新型频率驱动方式对液晶器件的显示有改善作用,将开拓液晶显示器件的新应用,具有实际应用价值.     

二级级联式室内可见光通信光学接收天线设计

针对室内可见光通信系统的传统光学接收天线无法同时满足高增益和大视场的问题, 设计了一种二级级联式光学天线. 通过分析信噪比、通信速率与接收天线视场角的关系, 发现视场角为40°–60°的光学天线最适用于室内可见光通信系统. 通过光学仿真软件TracePro的模拟及计算, 给出了所设计的二级级联式光学天线的增益随信号光入射角的变化关系. 结果表明, 相较于传统接收天线, 二级级联式光学天线具有更好的光学性能, 视场角为菲涅耳透镜单独接收时的4 倍. 利用Matlab对二级级联式光学天线竖直向上时的接收功率分布进行仿真, 结果显示探测器接收到的信号功率提升效果明显, 平均值较直接探测时增大了7 dBm, 进一步证实该二级级联式光学天线适用于室内可见光通信系统.     

光学元件残余偏振测量方法与装置

光学镜头的残余偏振是影响偏振遥感探测、偏振军事目标识别和精密光学测量仪器测量准确度的一个关键参数。针对大口径可见光波段光学镜头偏振度准确测量的问题,研制了一台光学镜头残余偏振度测量装置。该装置利用表面镀金属膜的大口径离轴抛物面反射镜作为准直光源,通过控制入射光的入射角、降低入射光源的残余偏振度等技术,在水平、垂直、45°、135°的方向获得了一致性很高的斯托克斯参量。为了验证该装置的性能,对可见光波段口径小于160 mm的光学镜头残余偏振进行了实际测量,测量结果表明,该测量装置的残余偏振度低于0.2%,可满足高精度光学镜头残余偏振的测量需要。     

Nonlinear adaptive filters for high-speed LED based underwater visible light communication [Invited]

Underwater visible light communication(UVLC) is expected to act as an alternative candidate in nextgeneration underwater 5 G wireless optical communications. To realize high-speed UVLC, the challenge is the absorption, scattering, and turbulence of a water medium and the nonlinear response from imperfect optoelectronic devices that can bring large attenuations and a nonlinearity penalty. Nonlinear adaptive filters are commonly used in optical communication to compensate for nonlinearity. In this paper, we compare a recursive least square(RLS)-based Volterra filter, a least mean square(LMS)-based digital polynomial filter,and an LMS-based Volterra filter in terms of performance and computational complexity in underwater visible light communication. We experimentally demonstrate 2.325 Gb/s transmission through 1.2 m of water with a commercial blue light-emitting diode. Our goal is to assist the readers in refining the motivation, structure,performance, and cost of powerful nonlinear adaptive filters in the context of future underwater visible light communication in order to tap into hitherto unexplored applications and services.     

Frustrated-total-internal-reflection-based thin-film color separator

The frustrated-total-internal-reflection thin-film color filtering device operating in a visible spectral range is designed. Such a device splits an incident light beam into spatially separated red, green, and blue color beams. Spectral shape and angular spread of transmitted light for s and p polarizations are calculated at different values of refractive indices and thicknesses of layers.     

Proposal for an optical laser producing light at half the Josephson frequency

We describe a superconducting device capable of producing laser light in the visible range at half of the Josephson generation frequency with the optical phase of the light locked to the superconducting phase difference. It consists of two single-level quantum dots embedded in a p-n semiconducting heterostructure and surrounded by a cavity supporting a resonant optical mode. We study decoherence and spontaneous switching in the device.